Field of the Invention
The present invention relates to a measuring apparatus for measuring a reflection characteristic of a surface.
Description of the Related Art
Conventionally, it is an important proposition to evaluate a printed product, a painted surface, and an exterior of a product, and JIS and ISO set standards for measuring a reflection characteristic of an object surface (surface) such as gloss. For example, as standards for measuring a specular gloss, JIS Z 8741 and the like are set. As standards for measuring a haze which represents a degree of image unclearness (dullness of a sample surface), ISO13803, ASTM E 430, and the like are set. As standards for measuring distinctness-of-image gloss associated with gloss, ASTM E 430, ASTM D 5767, and the like are set. As standards for measuring an image clarity (image clearness), JIS K 7374, JIS H 8686, and the like are set.
In respective standards, since there are surfaces suitable and unsuitable for measurement, the user has to select an optimal standard from the aforementioned standards depending on the situation, so as to measure the reflection characteristic. FIG. 6 shows a specular gloss measuring method defined in JIS Z 8741. A light beam from a light source 1 is roughly condensed by a lens 2 to be condensed on a rectangular light source slit 31, which is set to have an aperture angle defined by the standard, and the light source slit 31 forms a secondary light source having the defined aperture angle. A light beam from the light source slit 31 is converted into a nearly parallel light beam by a lens 41, and a surface 10 is irradiated with the nearly parallel light beam. Light reflected by the surface 10 has a unique reflection pattern depending on a state of the surface 10, and is condensed again by a lens 42, thus forming an image of the light source slit 31 on a light-receiving slit 32. Light, which has passed through the light-receiving slit 32, enters a light-receiving element 100, and is output as a photoelectric signal from the light-receiving element 100. A specular gloss measuring apparatus shown in FIG. 6 calculates a glossiness of the surface 10 using a relative intensity between the amount of light reflected by the surface 10 and an amount of light reflected by a reference surface, which amount is measured in advance. The specular gloss measuring apparatus shown in FIG. 6 can define brightness of reflection of a light source, but does not define a blurred degree of reflection of a light source, and cannot perfectly express the state of the surface 10.
FIG. 7 shows the arrangement of an apparatus for measuring a haze defined by ASTM E 430. A light beam from a light source 1 is roughly condensed by a lens 2 to be condensed on a light source slit 31, which is set to have an aperture angle defined by the standard, and the light source slit 31 forms a secondary light source having the defined aperture angle. A light beam from the light source slit 31 is converted into a nearly parallel light beam by a lens 41, and a surface 10 is irradiated with the nearly parallel light beam. Light reflected by the surface 10 has a unique reflection pattern depending on a state of the surface 10, and is condensed again by a lens 42, thus forming an image of the light source slit 31 on a light-receiving slit 33. Light, which has passed through the light-receiving slit 33, enters a light-receiving element, and is output as a photoelectric signal. The light-receiving slit 33 includes three slits 33a, 33b, and 33c, which are set at 18.1°, 20°, and 21.9° with respect to a perpendicular to the surface 10. The slit 33b is used to measure a specular gloss, and the slits 33a and 33c are used to measure a haze. The haze is an index indicating a degree of image unclearness. However, since an angle difference from specular reflected light of the slits 33a and 33c is small, a state of the surface 10 suitable for measurement of a haze is limited. When a reflection image exhibits unclearness beyond recognition, it is difficult to calculate a haze from the measurement result of the measuring apparatus shown in FIG. 7.
A distinctness-of-image gloss is measured using an apparatus having the same arrangement as that shown in FIG. 7 except for dimensions of the slits and a value calculation formula. More specifically, angles of the slits 33a, 33b, and 33c with respect to the perpendicular to the surface 10 are 19.7°, 20°, and 20.3°, and slit sizes are different. Like in measurement of a haze and the like, it is difficult for the surface 10 whose reflection image exhibits unclearness beyond recognition to calculate a distinctness-of-image gloss.
FIG. 8 shows the arrangement of an apparatus used in an image clarity test method defined by JIS K 7374. A light beam from a light source 1 passes through a slit 31 and enters a lens 41 to be converted into parallel light, with which a surface 10 is irradiated. Reflected light by the surface 10 has a unique reflection pattern depending on a state of the surface 10, and is condensed again by a lens 42, thus forming an image of the light source slit 31 on a comb-tooth slit 50. The comb-tooth slit 50 is configured by five types of slits having different pitches. Contrast values are acquired by calculating maximum and minimum transmitted light amounts upon moving the comb-tooth slit 50 in a slit array direction, thus expressing the state of the surface 10 by five contrast values. Since the image clarity measuring method evaluates the clearness of a reflection image using contrast values, the brightness of the reflection image cannot be discussed.
Japanese Patent Laid-Open No. 2008-256454 describes an apparatus and method for measuring a specular gloss of a surface, and Japanese Patent Laid-Open No. 2007-24655 describes an apparatus and method for measuring an image clarity of a surface.
As described above, the measuring apparatuses defined by the respective standards have respective features, and measure different target reflection characteristics of a surface. Also, Japanese Patent Laid-Open Nos. 2008-256454 and 2007-24655 disclose the apparatuses and methods for measuring reflection characteristics of a surface. However, these apparatuses and methods can only measure limited reflection characteristics of the surface. Therefore, the user in need of various reflection characteristics of a surface, has to prepare for measuring apparatuses of a plurality of methods, and has to selectively use them depending on the situation. For this reason, the user requires cost for purchasing a plurality of apparatuses, and a place for housing the plurality of apparatuses, thus imposing a load on the user.